PURPOSE: To efficiently obtain the subject compound used for a synthetic raw material, etc., for teanin which is a flavor ingredient of tea by reacting a L-γ- glutamyl group-containing compound with a lower alkylamine in the presence of an enzyme having γ-glutamyltranspeptitase activity.

CONSTITUTION: A crude enzyme ingredient derived from Bacillus subtilis is dissolved in a 20mM tris buffer hydrochloride solution (pH 7.5) and sufficiently dialyzed to the buffer solution and an insoluble matter is removed by centrifugal separation and the resultant transparent liquid is passed through an anion exchange column and the absorbed material is eluted with an eluting liquid and ammonium sulfate is added at 0.8% saturated concentration to the eluted fraction and the mixture is allowed to stand at 4°C one night and then centrifuged to afford an enzyme having γ-glutamyltranspeptidase activity. The enzyme is added to 100mM carbonate buffer solution (pH10.0) containing a compound (e.g. L-glutamine) having L-γ-glutamyl group and lower alkylamine or its salt (e.g. ethylamine hydrochloride) and the compound having the glutamyl group is made to react with the lower alkylamine or its salt in the presence of the enzyme at 37°C for 18hr to provide the objective L-γ-glutamyl-lower alkylamine.